Fan cooling system



Sept. 4, 1945. H, HAGEN 2,384,088

FAN COOLING SYSTEM Filed June 29, 1943 2 Sheets-Sheet l To Baifcry.

171 verl Zor. HAROLD /-T HAGEN Patented Sept. 4, 1945 FAN COOLING SYSTEM Harold F. Hagen, Millis, Masa, assignor to B. F. Sturtevant Company, Boston, Mass.

Application June 29, 1943, Serial No. 492,713

18 Claims.

This invention relates to the cooling of heat exchangers in moving vehicles and relates more particularily to the cooling of internal combus- I tion engines used in aircraft.

This application is a continuation-in-part of my copending application, Serial No. 450,478, filed July 10, 1942.

It is the general practice to cool radial type airplane engines by the impact or ram of the air through which the airplanes are moving, against the surfaces of the engines. The higher powered engines are enclosed within cowls which act as air pumps in that differences in pressure are provided between the entrances to and the exits from the cowls, resulting in the flow of air over the cooling surfaces of the engines.

The cowis are provided with flaps at their air exit louvres which are adjustableto vary the discharge areas for varying the volumes of air through the cowls. The induction action of the flaps is also used at times for aiding the cowl action when its ram action is insufficient.

The work required for providing cowl action and flap action is taken from the propeller thrust. This work can be done more eflectlvely and more efliciently over a wide operating range, by propeller fans located within the engine cowls, the fans being designed and operated to provide all the pressure required for cooling, the cowis and the flaps providing no pressure and doing no work.

If such a fan is designed to do all the work at say 30,000 feet elevation, then at lower altitudes, due to the greater air densities, higher air pressures than are required are provided by the fan; the engine is overcooled, and the fan absorbs more power than is needed, from the engine. It is desirable therefore, to be able to vary the pressure provided by the fan in accordance with cooling requirements. This can be done by adjustable spin vanes located in the inlet to the fan. When lower air pressures are desired, the vanes are adjusted to give increased spin to the air entering the fan, this resulting not only in decreased air pressure from the fan but in decreased fan power.

When the fan is doing all the work, the rearward velocity of the air discharged from the exit louvres is at least equal to the velocity of the airstream past the airplane. It may be equal to the velocity of the propeller slipstream or at any velocity between the airstream and slipstream velocities. If it is discharged at velocities higher than the slipstream velocity, the additional work done is not required and represents a loss in engine emciency. If the air .is discharged at a velocity below the airstream velocity, then the cowl or the flaps are doing work; there is drag and a loss in engine efficiency.

It should be understood that where a cowl does work, the air entering the cowl has its velocity reduced by the resistance in its path so that the velocity of the air leaving the cowl exit louvres is considerably reduced below that of the airstream. The difference between the entering and the leaving velocity results in an undesired drag. When outlet flaps are used to increase the air flow by induction, there is considerable additional drag to be overcome. The relative velocities close to the flaps may be high but the static pressure due to the induction action of the flaps will be below atmospheric. Before the air can pass beyond the influence of the airplane, the pressure will have to be increased to that of the atmosphere and this requires additional energy.

While it is preferred to have a fan do all the work in cooling an airplane engine, it seems eco-. nomical to have cowl action aid a fan at extreme loads. For example, at altitudes from sea level to 30,000 feet, a fan may be provided to do all the work. Between 30,000 feet and 40,000 feet, cowl action may advantageously be used for aiding the fan.

A feature of this invention resides in providing a fan for cooling'a heat exchanger such as an airplane engine; in varying the volume of air provided by the fan under thermostatic control, and within the range where the fan can do all the work, automatically varying the air exit area of the cowl for maintaining the air discharged at a velocity which will result in minimum engine power.

Another feature of this invention resides in providing, when the fan has been adjusted to do maximum work and the engine requires additional cooling, that the automatic control of the velocity of the air discharged from the cowl be discontinued and that the thermostatic control then adjust the air exit area of the cowl for modifying the cowl action in accordance with cooling requirements.

An object of the invention is to reduce the power required for cooling heat exchangers in moving vehicles.

Another object of the invention is to control the air volumes supplied'by a fan for cooling a heat exchanger in a moving vehicle, in accordance with variations in temperature of the heat exchanger, and to maintain the air leaving the heat exchanger and merging into the air stream passing the exterior of the vehicle at a velocity which will result in minimum engine power.

The invention will now be described with ref- I erence to the drawing, of which: I I

Fig. 1 is an elevation view, partially in section of an air cooled airplane engine mounted within a cowl; having a propeller fan within the cowl, and having spin vane controls and flap controls embodying this invention;

Fig. 2 is a schematic diagram illustrating the controls of Fig. 1 together with control and energizing circuits therefor;

Fig. 3 is a schematic diagram of the wiring of the relays of Fig. 2, and

Fig. 4 is a sectional view of the form of diaphragm chamber 66 which would probably be used instead of the one illustrated diagrammatically by Fig. 2, for compensating for the effect of the heated air discharged from the cowl.

Fig. 1 illustrates the application of this in vention to the cooling of an airplane engine. The engine 6 is a conventional, radial, air cooled engine, and while for the convenience of illustration, it is shown as having a single row of cylinders, it may, of course, have two rows of cylinders as have the higher powered engines to which this invention is particularly applicable. The conventional propeller I having the streamlined hub 8, is mounted on the outer end of the engine shaft 9.

The cowl I is around the engine 6 and at its front or upstream end has the inner wall l2 which forms the chamber l3 for enclosing the spin vane adjusting mechanism indicated generally by Id.

The propeller fan I is mounted on the shaft 9 adjacent the engine 6. This fan preferably is similar to that disclosed in my copending application, Serial No. 357,767, filed September 21, 1940. The blades of the fan l5 have airfoil sections as disclosed in said application with chords which decrease in width from base to tip as illustrated by Fig. 1.

The spininducing vanes 26 are mounted in the entrance to the cowl between the propeller 1 and the fan I5. The bases of the vanes 26 are secured to the rods H, the lower ends of which are pivoted in the outer housing of the bearing l8 for rotation therein. The bearing i8 is supported by the shaft 9 and serves to support the inner ends or bases of the vanes 26.

The vanes 26 are attached at their tips to the rods I9 which are pivoted in the inner wall l2 of the cowl I 0. The rods l9 have mounted therein the bevel gears 2| which mesh with the bevel gears 22 which are mounted on the levers 23. The levers 23 of all of the vanes are interconnected by linkage as disclosed in my Patent No. 1,989,413 which issued January 29, 1935, whereby all vanes may simultaneously be rotated.

The vanes are rotated by the motor 25 to the shaft of which the uppermost of the bevel gears 22 is attached.

The vanes 26 may be adjusted from a position where the maximum desired spin is imparted to the air entering the fan to wide open position where they have no effect upon the air. As the spin is increased, the volume of air moved by the fan is decreased and the power required by the fan is correspondingly decreased.

The vanes may be adjusted to provide counter spin for increasing the air pressure over that which could be provided by the fan alone. Thus they may be adjusted, for example, from counter spin positions of say 35 to spin inducing angles of say In the following description Vx is to be imderstood as representing the difierence in velocity between that of the air stream moving past the airplane, and that of the air discharged from the cowl 'back into the atmosphere. When the fan is doing all the work, it is preferred that the velocity of the air discharged from the cowl be that of flight, or that it have a value between the velocity of flight and the absolute velocity of the propeller slipstream. Between these two cowl discharge velocities, the fan will emciently aid the propeller thrust in moving the airplane through the air.

The thermostat 21 which responds to engine temperatures adjusts the vanes 26 by the motor 25 to open the vanes when the engine is'too hot and to move the vanes towards closed position when the engine is too cold.

During the time the thermostat 21 is in control of the vanes, the impact tube 52 which is exposed to the airstream velocity, and the impact tube 53 which is exposed to the velocity of the air in the exit louvres 54, adjust the flaps 5i by the motor 50 to maintain Vx=0 throughout the range of adjustment of the vanes. Vx would vary with variations in the speed of the airplane and with variations in the air volume supplied by the fan if these controls were not provided.

When the vanes have been opened to extreme wideopen position or counter spin position, the limit switch armature 32 is moved by the cam 4| on an extension on one of the pivot rods of one of the vanes 26 to open the circuit of the thermostat to stop the motor 25. At the same time, the armature 60 closes 'the energizing circuit of the relay solenoid 55 which acts to disconnect the vane closing contacts of the thermostat 21 from control of the vane adjusting motor 25 and places the thermostat in control of the motor 59 which adjusts the flaps 5|. The motor 50 then adjusts the flaps towards open position for aiding in the cooling action when the engine is too hot and draws the flaps in wardly when the engine is too cold.

When the thermostat is satisfied after having been in control of the flaps, it opens contacts which cause the solenoid 55 to become deenergized and restores the thermostat to control of the spin vanes and the impact tubes to control of the flaps.

If the engine becomes too cool, the thermostat closes controls which cause the motor 25 to rotate the vanes towards closed position. The cam 4| is rotated so that the limit switch armature 32 is released to strike the contact 3| and to close the circuit to the thermostat 21 which will also permit the motor 25 to again rotate the vanes towards open position.

Limit switches are provided for opening the control circuits of the motor 50 for preventing operation of the motor when the flaps are adjusted to either of the two extreme positions. A limit switch is also provided for opening the control circuit of the motor 25 for preventing operation of the motor after the vanes have been adjusted to fully closed position.

All limit switches while preventing the opera- 'tion of the motors in one direction do not however, prevent their operation in the. other direction so that, for example, while the thermostat may act to prevent the motor 25 from trying to continue to open the vanes when they are fully open, it is still in condition to operate the motor in the other direction. In other words, the mo-- tors are not disconnected from the battery by the limit switches.

The detail operation of the circuits of Figs. 2 and 3 will now be described.

The motor rotates the spin vanes 28 towards open or closed position, depending upon the direction of rotation of the motor.

The thermostat 21 which may be of the bellow type, has the arm 24 to which are attached the armatures 28 and 58 which are electrically insulated from each other. When the engine temperature is too high, the armature 28 moves to the rightwith reference to Fig. 2 of the drawings and strikes the contacts 28 and I84, and the armature 58 moves to strike the contacts 58 and 84. When the engine is too cool, the armature 28 is moved to the left against the contacts 42 and I88 and the armature 58 is moved away from the contacts 58 and 84. When the thermostat is satisfied, the armatures 28 and 58 are separated from their associated contacts.

The thermostat 21 is normally in control of the motor 25. When the engine temperature is too high, the thermostat moves its armature 28 to the right, causing it to strike the contact 28 for causing the motor 25 to rotate in a direction to open the vanes. This is accomplished by the armature 28 closing a circuit including the contact 28, the wire 38, the contact 3|, the limit switch armature 32, the wire 33, the relay 34, the wire 35 and the armature 28. Electric current is supplied from the battery 38 to the relay 34 through the wires 31, 38, 38, and 48. The relay connects the field winding of the motor 25 to its armature as illustrated by Fig. 3, so that the motor rotates the vanes towards open position.

The drawings illustrate the vanes as having been adjusted to their extreme open or counter spin position. The limit switch armature 32 has been moved to the left by the cam 4| on the extension 42 of one of the vane pivot rods. This has caused the armature 32 to move away from the contact 3|. opening the above described c rcuit and stopping the motor 25.

If the engine is too cool, the thermostat 21 will move its armature 28 to the left causing it to strike the contact 42 and to close the circuit including the contact 42, the wire 43, the limit switch contact 44 and the armature 45, the wire 48, the relay 34 the wire 35 and the armature 28. This causes the relay to connect the field of the motor 25 to its armature in reverse to its previous condition so that the direction of rotation of the motor 25 is reversed so that it adjusts the vanes towards closed position. Ii. the thermostat is not satisfied before the vanes reach the fully closed pos tion, the previously described cam 4| moves the limit switch armature 45 away from its contact 44 when the vanes are fully closed, thus open ing the last described circuit and stopping the motor 25.

During the time the thermostat 21 is in control of the spin vanes, the motor 58 acts to adjust the flaps 5| in the exit louvres 54 so that Vx=0. The flaps 5| are conventional flaps interconnected so that adjustment of one aflects adjustment of all.- The impact tube 52 is exposed to the airstream velocity or to the slipstream velocity whichever may be preferred, and the impact tube 53 is exposed to the velocity of the air in the exit louvres. When the velocities at the two impact tubes are equal, then Vx=0. If they become unequal as the spin vanes are adjusted, then the control now to be described causes the motor 58 to adjust the flaps for so changing the velocity of the air from the exit louvres so that throughout the entire range of adjustment of the spin vanes by the motor 25, Vx=0. The motor 58 has a threaded shaft 82 which rotates within the screw jack 58 which has internal threads meshing with the threads on the shaft 62 so that upon rotation of the shaft 82, the jack 58 is moved towards or away from the motor depending upon its direction of rotation.

The screw jack 58 is slidably attached to the base 83. One end of the connecting rod 84 is rotatably attached to the jack 58 and its other end is rotatably attached to the crank arm 85 attached to one of the flaps 5|. When the motor 58 rotates its shaft 82 in one direction, the jack is advanced away from the motor to place through the connecting rod 84 and the crank arm 85, the flaps 5| out into the slipstream as illustrated by the lower dotted outlines of Fig. 2. In this position, the cowl is wide open and its action is maximum. When the shaft 82 is rotated in the other direction by the motor 58, the jack is moved towards the motor and acts to draw the flaps inwardly into the exit louvre 54 as illustrated by the upper dotted outline of Fig. 2, so as to restrict the space between the flaps and the air guiding edge 86 of the structure, thereby causing an increase in the velocity of the air through the louvre 54.

The impact tubes 52 and 53, when the thermostat 21 is in control of the spin vanes, act to control the motor 58 for adjusting the flaps so that VX=0. The impact tube 52 connects into the diaphragm chamber 68 on one side of the diaphragm 81 while the impact tube 53 connects into the chamber 68 on the other side of the diaphragm.

The diaphragm 81 has connected thereto, the contact arm 68 which when the airstream velocity is greater than that of the air from the exit louvres, moves to the right (facing Fig. 2) against the contact 88, closing a circuit including the contact 88, the wire 12, the contact 13, the armature 14, the wire 15, the wires 18, the limit switch 1|, the relay 16, the wire 11, and the contact arm 68 of the diaphragm 61. This connects as shown by Fig. 3, the field and armature of the motor 58 together for causing the motor 58 to rotate in a direction to draw the flaps 5| inwardly for restricting the outlet passage for increasing the velocity of the air therethrough. During the operation just described, the thermostat 21 would be in control of the spin vanes so that the cam 4| would not have moved the limit switch armature 88 against the contact 6| for energizing the solenoid 55, so that the solenoid 55 would be deenergized and the armatures 14 and 8| would be against the contacts 18 and 88 respectively.

If the velocity of the air from the exit louvres is greater than that of the airstream than that of the airstream, then the diaphragm 81 will move to the left and will move the contact arm 88 against the contact 8|, closing a circuit including the contact 8|, the wire 88, the contact 88, the armature 8|, the wire 82. the wires 82, the limit switch 83, the relay 18, the wire 11, and the diaphragm contact arm 88. This would connect the field and armature of the motor 58 to reverse the direction of rotation of the motor causing it to move the flaps 5| outwardly until the diaphragm 81 reaches mid-position at which time the circuit is disconnected.

When the motor 25 under control of the thermostat 21 has adjusted the vanes to maximum spinposition, the cam-4l movesthe-limit switch armature 45 away from the contact 44 and opens the circuit including the wire 43, the contact 42, the thermostat armature 20, the wire 35, the relay 34, the wire 45, the limit switch armature 45, and contact 44, thus opening the circuit which energizes the motor 25 to rotate in a direction to close the spin vanes.

The motor 25 will be energized to rotate in the opposite direction for adjusting the spin vanes towards open position when the engine requires cooling and the thermostat accordingly moves its arms 29 against the contact 29 as previously described.

When upon a demand by the thermostat 21 for cooling, the spin vanes have been fully opened and the engine is still too hot, the cam 4| moves the armatures 32 and 90 to the left (facing Fig. 2) causing the armature 32 to open the previously described circuit including the contact II, for stopping the motor 25, and causing the armature 60 to strike the contact 6| and to close the circuit including the contact the wire 99, the contact 50, the armature 59, the contact, the wire 90, the solenoid 55, the wires 31 and 39, the battery 35, and the wire 01 and the armature 60, causing the energization of the solenoid 55 and causing its armature 9| to be pulled away from the contact 90 and against the contact 91, and causing the armature 14 to be pulled away from the contact 19 and against the contact 99.

This disconnects the impact tubes 52 and 53 and the diaphragm 61 from control of the flap adjusting motor 50 and places the motor 50 under control of the thermostat 21 as has been described.

The thermostat 21 then adjusts through the motor 50, the flaps outwardly for increasing the volume of air through the cowl and for producing the induction of air from the exit louvres by the flaps if this is desired.

If the engine is too warm, the thermostat 21 moves its armature 20 against the contact I04, closing the circuit including the contact I04, the wire I05, the contact 99, the armature I4, the wire I5, the wires I0, the limit switch 'II, the relay 15, the wire I1, the wire I8, the armature 28 and energizing the motor 50 to rotate in a direction to move the flaps 5| into the slipstream as has been described.

If the engine is too cold, the thermostat 21 moves its armature 29 against the contact I00, closing the circuit including the contact I05, the wire I03, the contact 91, the armature 9|, the wire 92, the wires 82, the limit switch 83, the relay 16, the wires 11 and I8 and the armature 28. This energizes the motor to rotate in a direction to draw the flaps in towards closed position.

The armature 59 on the thermostat arm 24, and its associated contacts 50 and 84 are in the energizing circuit of the solenoid 55 which as has been described, switches the thermostat to control of the flaps when the spin vanes are wide open and the engine is still too hot. When the thermostat becomes satisfied while in control of the flaps, its armature leaves the contacts 58 and 94 and opens the deenergizing circuit of the solenoid 55, causing it to restore control of the spin vanes to the thermostat and the control of the flaps to the impact tubes.

The limit switch II serves to stop the motor 50 to prevent it from attempting to draw the vanes inwardly when they have reached their ex- 51, on -the;;.|ackscrew 59 and by, the opening of outward position. This is accomplished by the treme inward position. This is accomplished by the opening of the limit switch II by the lever opening of the switch 03 by the lever 51 on the jack screw 59 and the opening of the previously described circuit including the switch 93. The opening of the limit switch while it stops the motor 50 from rotating in one direction, will not prevent the motor from rotating in the other direction when the controls call for same. The same applies to the limit switch 93.

Fig. 3 illustrates the internal circuits of the relays 34 and I6 and the connection of their components to the fields and armatures of the motors 25 and 50 respectively for causing the reversal thereof when the motor controls call for reversal. It will have been observed that the center wire of the three wires entering the lower side of the relay 34 and of the three wires entering the upper side of the relay I8, is connected to a control contact arm (of the thermostat 2'! or of the diaphragm 91). The wires on each side of the center wire lead to contacts so that upon movement of a control contact arm in one direction, a circuit is closed between the center wire and one of the side wires and upon movement 0! the control contact arm in the other direction, a circuit is closed between the center wire and the other of the side wires.

When a circuit is closed between the center wire 0 and the outer wire III, the solenoid H2 is energized by the battery. This causes the solenoid armatures H3 and 4 to be pulled down against the contacts 5 and 5 respectively. The contacts II 5 and H9 are connected to the armature III of a motor. The soleniod armatures H3 and 4 are connected to the battery so that upon energization of the solenoid II 2, the motor armature III is connected to the battery. The motor field winding I I0 is connected directly to the battery so that upon energization of the solenoid I I2, the armature and field of the motor are connected together and to the battery and the motor rotates in one direction.

When the circuit is closed between the center wire II 0 and the outer wire II9, the solenoid. I20 will become energized by the battery. The solenoid 2 will be deenergized since at this time, the control contact arm will have moved to open the circuit between the wires 0 and III. Upon energization of the solenoid I I2, the armatures H3 and 4 will be pulled upwardly to strike the contacts I2| and I22 respectively. The contacts |2| and I22 are connected to the motor armature I I but in such a way that the armatures II3 and I connect the motor armature to the battery in reverse to the connection through the previously described contacts H5 and H9 so that the motor is energized to rotate in a direction reverse to that it rotates when the solenoid I20 isenergized.

It is recognized that the air through the exit louvres 54 is heated and expanded by heat from the engine and that this should be taken into account. It seems desirable therefore, that the diaphragm chamber 66 be constructed as illus-.

being interconnected by the lever ii! for simultaneous movement.

While in the foregoing, the cowl has been described as doing work during peak loads, the invention is not limited to having the cowl do any work. The adjustment of the spin vanes for volume control and the adjustment of the area of the air exit louvres for maintaining Vx= comprise features of this invention which may be used when the fan is designed to do all the work at all loads.

These is seen to be an increased saving in engine power as Vs varies from a positive value to zero due to reduction in drag. This invention decreases the drag by increasing the velocity of the air discharged from the cowl to approach a velocity between that of flight and that of the propeller slipstream.

In the annexed claims, airstream means the air passing the exterior of the vehicle or airplane,

and in the case of a vehicle having a tractor propeller, may be the propeller slipstream, and relative velocity" means the velocity of the vehicle or airplane relative the airstream as distinguished from the velocity relative the earth.

While one embodiment of the invention has been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangement of apparatus illustrated, as modifications thereof may be suggested by those skilled in the art without departure from the essence of the invention.

What is claimed is:

1. A system for cooling a heat exchange surface in a vehicle moving through air, comprising means defining an air passage for taking in air from the direction of movement of the vehicle and for discharging the air from the vehicle towards the rear thereof, said passage enclosing said surface, a fan in said passage for moving air therethrough, means for controlling the volume of air moved by said fan, means including means responsive to variations inthe temperature of said surface for adjusting said volume control means for varying the volume of air through said passage, means for varying the air discharge area of said passage, and means including means responsive to variations in the relative velocity between said vehicle and the airstream for adjusting said discharg area varying means.

2. A system for cooling a heat exchange surface in a vehicle moving through air, comprising means defining an air passage for taking in air from the direction of movement of the vehicle and for discharging the air from the vehicle towards the rear thereof, said passage enclosing said surface, a fan in said passage for moving air therethrough, means for controlling the volume of air moved by said fan, means including means responsive to variations in the temperature of said surface for adjusting said volume control means for varying the volume of air through said passage, means for varying the air discharge area of said passage, and means including means responsive to variations in the velocity of the air from said surface for adjusting said discharge area varying means.

3. A system for cooling a heat exchange surface in a vehicle moving through air, comprising means defining an air passage for taking in air from the direction of movement of the vehicle and for discharging the air from the vehicle towards the rear thereof, said passage enclosing said surface, a fan in said passage for moving air therethrough, means for varying the volume of air moved by said fan, means including means responsive to variations in the temperature of said surface for adjusting said volume control means for varying the volume of air through said passage, means for varying the air discharge area of said passage, and means including means responsive to variations in the relative velocity between said vehicle and the airstream and to variations in the velocity of the air from said surface for adjusting said discharge area varying means.

4. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan, means including means responsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan, and means including means responsive to the relative velocity between the airplane and the airstream for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl.

5. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan,

means including means responsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan, and means including means responsive to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl.

6. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan, means including means responsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan, and means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge areavarying means.

'7. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof,

comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan, means including means responsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan,

means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, and means including means actuated when said vanes have been adjusted to their maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control of said spin vanes and for connecting said temperature responsive means to control of said discharge area. varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for affecting additional cooling by action of said cowl.

8. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan, means including means responsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan. means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cow] for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, means including means actuated when said vanes have been adjusted to their maximum air volume position and said engine is still to hot, for disconnecting said temperature responsive means from control of said spin vanes and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for aifectlng additional cooling by action of said cowl, and means including means actuated when said area varying means has been adjusted for minimum cowl action and said engine is still too cool, for restoring control of said spin vanes to said temperature responsive means.

9. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan, means including means responsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan, means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, means including means actuated when said vanes have been adjusted to their maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control of said spin vanes and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for affecting additional cooling by action of said cowl, means including means actuated when said area varying means has been adjusted for minimum cowl action and said engine is still too cool, for restoring control of said spin vanes to said temperature responsive means, and means including means responsive to the relative velocity between the airplane and the airstream for varying the position at which said area varying means has been adjusted for minimum cowl action.

10. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan, means including means rsponsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan, means including means responsive to the relative velocity between the airplane and the airstr'eam and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, and

means including means actuated when said vanes have been adjusted to their maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control of said spin vanes, for disconnecting said velocity responsive means from control of said area varying means, and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for effecting additional cooling by action or said cowl.

11. A cooling system for an airplane engine having-a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan, means including means rseponsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan, means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharge from said cowl, means including means actuated when said vanes have been adjusted to their maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control of said spin vanes, for disconnecting said velocity responsive means from control 0 said area varying means, and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for aflecting additional cooling by action of said cowl, and means including means actuated when said area varying means has been adjusted for minimum cowl action and said engine is still too cool, for restoring control of said spin vanes to said temperature responsive means, and for restoring control of said area varying means to said velocity responsive means.

12. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, spin vanes in the inlet to said fan, means including means responsive to the temperature of said engine for adjusting said vanes for varying the volume of air moved by said fan, means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, means including means actuated when said vanes have been adjusted to their maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control of said spin vanes, for disconnecting said velocity responsive means from control of said area varying means, and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for affecting additional cooling by action of said cowl, means including means actuated when said area varying means has been adjusted for minimum cowl action and said engine is still too cool, for restoring control of said spin vanes to said temperature responsive means, and for restoring control of said area varying means to said velocity responsive means, and means including means responsive to the relative velocity between the airplane and the airstream for varying the position at which said area varying means has been adjusted for minimum cowl action.

13. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, volume control means for varying the volume of air moved by said fan, means including means'responsive to the temperature oi said engine for-adjusting said volume control means for varying the volume 01 air moved by said fan, means including means responsive to the relative velocity between the airplane and the airstream and to' the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cow], and means including means actuated when said volume control means has been adjusted to its maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control of said volume control means and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for ail'ecting additional cooling by action of said cowl.

14. A cooling system for an airplane engine having a cowl around the engine, said cowl hav-' ing means for varying the air discharge area thereofjcomprising a propeller fan in said cowl rotatable by said engine, volume control means for varying the volume of air moved by said tan, means including means responsive to the temperature of said engine for adjusting said volume control means for varying the volume of air moved by said fan, means including means responsive to the relative velocity between the airplane and the airstream and to the velocity 01' the air discharged from said cow] for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, means including means actuated when said volume control means has been adjusted to its maximum air volume position and said engine is still too hot for disconnecting said temperature responsive means from control of said volume control means and for connecting said temperature responsive means to control of said discharge area. varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for affecting additional cooling by action of said cowl, and means including means actuated when said area varying means has been adjusted for minimum cowl action and said engine is still too cool, for restoring control of said volume control means to said temperature responsive means.

15. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, volume control means for varying the volume of air moved by said fan, means including means responsive to the temperature of said engine for adjusting said volume control means for varying the volume of air moved by said fan, means including means responsive to the relative velocity between the air plane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity 01' the air discharged from said cowl, means including means actuated when said volume control means has been adjusted to its maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control of said volume control means and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area va ying means towards open position for ailecting additional cooling by action of said cowl, means including means actuated when said area varying means has been adjusted for minimum cowl action and said engine is still too cool, for restoring control of said volume control means to said temperature responsive means, and means including means repsonsive to the relative velocity between the airplane and the airstream for varying the position at which said area varying means has been adjusted for minimum cowl action.

16. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, volume control means for varying the volume of air moved by said fan, means including means responsive to the temperature of said engine for adjusting said volume control means for varying the volume of air,

moved by said fan, means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, and means including means actuated when said volume control means has been adjusted to its maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means for control of said volume control means, for disconnecting said velocity responsive means from control of said area varying means, and for connecting said temperature responsive means to control or said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for eflfecting additional cooling by action of said cowl.

1'7. A cooling system for an airplane engine having a cowl around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, volume control means for varying the volume of air moved by said fan, means including means responsive to the temperature of said engine for adjusting said volume control means for varying the volume of air moved by said fan, means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, means including means actuated when said volume control means has been adjusted to its maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control 01' said volume control means, for disconnecting said velocity responsive means from control of said area varying means, and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means toward open position for ail'ecting additional cooling by action of said cowl, and means including means actuated when said area varying means has been adjusted for minimum cowl action and said engine is still too cool, for restoring control of said volume control means to said temperature responsive means, and for restoring control of said area varying means to said velocity responsive means.

18. A cooling system for an airplane engine having a cow] around the engine, said cowl having means for varying the air discharge area thereof, comprising a propeller fan in said cowl rotatable by said engine, volume control means for varying the volume of air moved by said fan, means including means responsive to the temperature of said engine for adjusting said volume control means for varying the volume of air moved by said i'an, means including means responsive to the relative velocity between the airplane and the airstream and to the velocity of the air discharged from said cowl for adjusting said discharge area varying means for varying the velocity of the air discharged from said cowl, means including means actuated when said volume control means has been adjusted to its maximum air volume position and said engine is still too hot, for disconnecting said temperature responsive means from control of said volume control means, for disconnecting said velocity responsive means from control of said area varying means, and for connecting said temperature responsive means to control of said discharge area varying means, whereby said temperature responsive means acts to adjust said area varying means towards open position for afiecting additional cooling by action of said cowl, means including means actuated :when said area varying means has been adjusted for minimum cowl action and said engine is still too cool, for restoring control of said volume control means to said temperature responsive means, and for restoring control of said area varying means to said velocity responsive means, and means including means responsive to the relative velocity between the airplane and the airstream for varying the position at which said area varying means has been adjusted for minimum cowl action.

HAROLD F. HAGEN. 

